EFFECT OF SODIUM-OXIDE ON THE MORPHOLOGY AND BASICITY OF ALUMINA

Various samples of alumina were compared to study the effect of crystallinity and sodium impurity on alumina morphology and basicity. Carbon dioxide adsorption, followed by FT-IR and desorption (TPD), and COS hydrolysis test reaction were used. The decrease of surface area observed on rather amorphous samples after introduction of small amounts of sodium is ascribed to a better crystallinity due to migration of a part of Na+ into the bulk. The charge compensation phenomenon decreases the number of defects in the anion subnetwork. It also provokes a decrease of the number of OH groups which could explain the decrease of activity towards COS hydrolysis of the samples containing very small amounts of Na2O (<1000 ppm). For larger amounts, COS conversion and carbon dioxide experiments showed an increase in basicity.